Tow processing



Oct. 14, 1969 o. D. GREY 3,471,901

TOW PROCESSING Filed Sept. 12, 1966 3 Sheets-Sheet 1 (\WHUUHU] MUSUQ wSwEwGwmQ 0 1 m m w kmfl akmmomwuw @EQETQ N Q. R EV n T H 22% m D. D. GREY TOW PROCESSING Oct. 14, 1969 3 Sheets-Sheet 2 Filed Sept. 12, 1966 TOW PROCESSING I 3 Sheets-Sheet 5 Filed Sept. v12, .1966

United States Patent 3,471,901 TOW PROQESSING Donald D. Grey, Matthews, N.C., assignor to Celanese Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 12, 1966, Ser. No. 578,641 Int. Cl. Dtllb /08; D01h 5/00 US. Cl. 19-66 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the production of opened tows and relates, more particularly, to the production of cigarette filter tips.

Cigarette filter tips are usually made from crimped continuous artificial filaments combined into a tow or bundle consisting or several thousands of such filaments. Typically, the filaments are produced by dry-spinning a solution of cellulose acetate into an evaporative atmosphere to form a relatively small bundle of a number substantially parallel filaments and a number of these smaller bundles are combined to make a tow, which may contain, for example, about 5,000 to 30,000 filaments of about 1 to 20 denier per filament. The tow is then generally mechanically crimped to the extent desired so that the filaments are more or less adhered to each other in a wavy band or ribbon-like form, with the crests and vales of the crimp in adjacent filaments being in registry. This ribbon is then packed as a bale (usually by traversing it back and forth in a carton) which is shipped to the cigarette manufacturer, or to a manufacturer of filter rods who reships the rods to the cigarette maker.

In one method of making cigarette filter rods from cellulose acetate tow, the tow band is drawn from the bale through a banding jet where it is subjected across its width to one or more streams of air which help to spread the tow into a flattened band. The flattened tow then passes to a driven differential gripping device whose driven rolls serve, inter alia, to deregister the crirnped filaments of the tow, as well as to draw the tow through the banding jet. The resulting opened tow then preferably passes through a second banding jet to a plasticizerapplying device, then to driven delivery rolls, and from there to a rod-making machine, which typically includes a stationary, circular funnel-like trumpet (where the tow band is shaped to a circular cross-section) and a garniture at which the circular bundle is then covered with a wrapping (e.g. cigarette paper) and cut to the desired length, for example to a length of 4 inches. The resulting rods are later cut transversely to form the shorter lengths (e.g. inch lengths) used in cigarette filter tips.

In attempting to operate a system of this type at a high rate of speed (such as a speed above 800 feet per minute, e.g. about 1000 feet per minute corresponding to the production of about 3000 rods per minute), it is found that the resulting rods are not as uniform as desired. They vary in weight and circumference, for example, to a considerably greater degree than rods produced at lower speed. Thus, there will be correspondingly undesirable large variations in the smoking qualities of the individual filter tip cigarettes made from the rods produced at high speeds.

In accordance with one aspect of this invention, I have discovered that the variability resulting from high speed operation can be reduced considerably by the use of a novel tow-gripping mechanism positioned upstream of the differential gripping device.

One embodiment of the improved tow-gripping unit is illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic side view of the overall operation;

FIG. 2 is an end View of the tow-gripping mechanism looking in the direction of movement of the tow;

FIG. 3 is a side view of the tow-gripping mechanism, and

FIG. 4 is a top view;

FIG. 5 is a cross-sectional view of a ball bushing used in the tow-gripping mechanism and FIG. 6 is a detailed view of a ball circuit of the bushing of FIG. 5.

As indicated in FIG. 1, the tow band 1 is drawn from the bale 2 over a stationary guide rod 3, through a banding jet 4 where it is subjected across its width to one or more streams of air which help to spread the tow into a flattened band. For example, the tow band may have a width of about 34 inches before entering the banding jet 4 and a width of 6 inches on leaving that jet. The flattened tow then passes around stationary guide rods 6 and 7, and under stationary guide rod 8, to the tow-gripping mechanism 9. From there, it passes to a driven differential gripping device 16 whose driven rolls serve to draw the tow through the tow-gripping mechanism 9 and banding jet 4 as well as to deregister the crimped filaments of the tow, as more fully described below. The resulting opened tow then preferably passes through a second banding jet 17 (being thereby spread, for example, from a width of about six inches, on leaving the differential gripping device 16, to a final width of about 12 inches), to a plasticizer-applying device 18, then to driven delivery rolls 19, 21 and from there to a rod-making machine 22, which may be of conventional construction having a trumpet 23 and garniture 24. If desired, the plasticizer need not be applied before the tow reaches the delivery rolls; instead, a film of plasticizer may be placed on these rolls for application thereby to the tow passing over them.

The tow-gripping mechanism 9 includes a pair of elongated freely rotatable upper and lower rolls 31 and 32, each having a uniform smooth cylindrical outer surface for contacting the flattened tow 1 which, in passing 'between these rolls, is squeezed between them, the upper roll 31 being pressed resiliently downward as by the action of a pneumatic diaphragm device 33, while the lower roll 32 is mounted with its axis stationary. More particularly, the end shafts 34, 36 of the rolls 31, 32, respectively, are supported on roller bearing 37 and 38. The two lower bearings 38 are fixed (as by-screws 39) to a stationary vertical foundation plate 41, while each of the two upper bearings 37 is mounted at the ends of a vertical guide bar 42. These guide bars 42 extend through and are adjustably fixed to the ends of a rigid cross bar 43 which is, in turn, engaged at its center portion by a stem 44 extending downward from the pneumatic diaphragm device 33. The vertical guide bars 42 may be fixed to the cross bar 43 by means of nuts 46 engaging screw threads 47 on the lower ends of the guide bars; a similar nut and screw arrangement 48 may be used for adjustably fixing the stem 44 to the cross bar.

The foundation plate 41 has a long slot 51, aligned with the nip of the rolls 31, 32 for. the passage of the tow through the plate. This slot 51 is open at one end 52 to permit easy insertion of the tow band, through said open end 52, into the desired position between the rolls 31, 32.

3 Thus, in effect, the lower roll 32 is mounted on an arm 53 extending from the lower part of the plate 41.

The smooth circular upper portions of the guide bars 42 are laterally supported and aligned (so that these bars, and the upper roll 31 carried thereby, move in a precise vertical path) by means of ball bushings 56 fixed (as by screws 57) to the foundation plate 41. Each of these ball bushings (see FIGS. and 6) comprises a generally cylindrical sleeve 58 carrying a large number of recirculating bearing balls 59 which are in rolling contact with the inner wall of the sleeve and with the outer surface of the guide rod 42 which passes through the sleeve. A retainer 61 within the sleeves holds the balls in place and separates them into three or more sets, establishing a corresponding number of oblong circuits for the balls. FIGS. 5 and 6 show details of one such circuit. In the load-carrying portion 62 of a circuit, the balls roll freely in a straight line path parallel to the axis of the sleeve (and to the axis of the guide rod). In the remaining, recirculating portion 63 of a circuit, the balls do not make contact with the guide rod but, instead, roll freely between the inner surface of the sleeve and a runway 64 provided by the retainer 61. Preferably, an adjustable ball bushing is used; in one form of adjustable bushing, the sleeve 58 is not a complete cylinder but has a slot 66 running its full length parallel to the axis and is housed in a split pillow block 56 (FIGS. 2 and 4) having an adjusting screw 68, which generally is tightened only enough to make the balls just grip the guide rod 42, to give a line-to-line or slight preload fit.

The apparatus may include means for returning the upper roll 31 to its upper position, such as helical springs 71 which are compressed between collars 72 (at the tops of the guide rods 42) and spring retainers 73 resting on the ball bushings 56. For example, when it is necessary to insert, or remove, the tow band from the tow-gripping mechanism, e.g. during start-up, the air supply to the pneumatic diaphragm device 33 may be shut off or vented (e.g. from a suitable valve 76 leading to the air supply tube 77 of the diaphragm device) so that the upper rod can rise under the influence of the springs 71 to a position permitting free passage of the tow between the rolls 31, 32.

The rolls 31, 32 have a relatively small mass and, therefore, a low inertia, so that they will respond quickly to changes in the tension in the tow and will permit start up without so loading the tow as to cause undesirable stretching or breaking of the tow. In a preferred embodiment, illustrated in the drawing, the upper and lower rolls are each 8 inches long (plus the stub shafts, at each end, which are each about inch long) and are each less than 2 (e.g. 1 /2) inches in diameter; the upper roll is of solid steel while the lower roll is similar but includes a rubber surface layer 78 (e.g. of Shore 8O hardness, A; inch thick); each roll weighs less than 5 pounds (e.g. about 3 to 4 pounds).

The pneumatic diaphragm device 33 is of known type having an air chamber, one wall of which is a flexible diaphragm (not shown) attached to the stem 44; air under adjustably controlled pressure is supplied to the air chamber through the tube 77. The diaphragm device is rigidly supported on the foundation plate 41 by means of a mounting bracket 79.

In operation, the tow is threaded through the apparatus while the upper roll 31 is in its upper, inactive, position and, with all the driven rolls in operation, the pressure in the diaphragm device is gradually increased so as to force the upper roll down against the tow thus increasing the tension in the tow band running between the nip of rolls 31, 32 and the differential gripping device 16 until that tension is just below that which would cause breakage of individual filaments; undesirably high tensions which can result from the use of too high a pressure at the nip, evidence themselves by the appearance of broken filament ends projecting slightly from the tow, like little hairs, so that the tow leaving the pretensioning device has a rough, unshaven appearance. When the air pressure is adjusted to the most desirable level for the particular tow, the tow band leaving the nip of the rolls 31, 32 has no visible broken filament ends and the crimp in its individual filaments is clearly visible.

Particularly suitable types of differential gripping devices 16 are described in Dunlap et al., US. Patent 3,156,- 016, whose disclosure is incorporated herein by reference, in which the tow is opened by subjecting it, while moving in a predetermined path, to a differential gripping action between a plurality of points spaced from one another both longitudinally and transversely of the path, so that certain laterally spaced sections of the tow are positively gripped relative to other laterally spaced sections of the tow, alternating with the said gripped sections, which are not gripped at all or are gripped at different relative points. In this manner; there is produced, as a function of the dilferential positive gripping of the tow, a relative shifting of adjacent filaments longitudinally of the tow, whereby the crimps are moved out of registry with one another. Preferably, although not necessarily, the differential gripping action is such that a relative lateral displacement between adjacent filaments of the tow is also effected, so that the combination of two transverse filament movements brings about the complete opening of the tow.

The differential gripping action may be achieved by the provision of at least one pair of rolls, one of which is smooth-surfaced and the other of which is grooved over its entire periphery; if desired, there may be a plurality of such pairs of rolls arranged in tandem. On each grooved roll, the grooves and the ridges alternating therewith may extend obliquely or helically in opposite senses from its center to its opposite ends. Thus, when the tow passes between the two rolls of any given pair of one grooved and one smooth-surfaced roll, some of the tow sections are gripped between the peaks of the ridges of the grooved roll and the outer peripheral surface of the opposed smooth-surfaced roll, while other sections of the tow which are at that time located in registry with the spaces between the ridges of the grooved roll are not gripped between the latter and the smooth-surfaced roll. Generally, only one roll of each pair is positively driven while the other is yieldably biased toward it and rotates due to the passing of the tow between the rolls.

I prefer to use two sets of differential gripping rolls, rather than the three sets specifically illustrated in the drawing of the previously mentioned Dunlap et al. patent. In a preferred embodiment, each set of rolls comprises an upper patterned-surface roll 81, 82 and a lower positively driven rubber-surfaced roll 83, 84, each upper roll being mounted for free rotation and being driven by the rotation of the corresponding driven lower roll. In one specific form, the rolls 81, 82, 83, 84, are each about 6 /2 inches in diameter and the upper rolls are of steel helically threaded with about 14 threads per inch, the thread being about & inch deep; the upper delivery roll 19 is about 3 inches in diameter, the lower delivery roll 21 is about 8 inches in diameter, both delivery rolls being of steel and the lower one being positively driven, the tow making an S-wrap about the rolls 19, 21; the roll 84 is driven at a surface speed greater than that of the roll 83 while the delivery roll 21 is driven about the same speed as the roll 83; thus when rolls 83 and 21 are driven at a surface speed of about 1000 feet per minute, the surface speed of roll 84 is, for example, about 1600 feet per minute. The

distance between the nip of rolls 81, 83 and the-nip of rolls 31, 32 is typically about one foot.

Even at high tow speeds the tow band approaching the rolls 81, 83 is much-flatter, smoother, and more free of random splits when our novel tow-gripping mechanism 9 is employed.

By the use of the ball bearing slide arrangement, the roll 31 is maintained in parallel alignment with roll 32 at all times despite vibrations and stresses resulting from high speed operation; its axis can move freely (in a fixed path in such parallel alignment), against the pressure exerted by the diaphragm device, in response to the forces accompanying such operation. When this ball bearing slide arrangement is used with rolls of low inertia, which respond quickly to changes in the tension in the tow, particularly good results are obtained.

It is within the broader aspects of this invention to use patterned-surface rolls having other configurations, such as the specific configurations illustrated in US. Patent 3,255,506, in the differential gripping device.

The banding jets 4 and 17 may be of well known type, in which the tow passes between a pair of spaced parallel plates (placed, for example, inch apart), one or both ofwhich have a plurality of slots leading from a compressed air plenum chamber, so that streams of air are blown at the tow through the slots. The degree of uniformity of the filter rod may be gauged, as the machine is running, by observing the variability of the width of the tow band leaving the second banding jet; this variability is much lower when the tow-gripping mechanism of the present invention is used.

In the plasticizer applying device 18, the plasticizer may be delivered by means of a conventional spray head, but more preferably by means of a plurality of rapidly whirling disks which centrifugally project fine droplets of the plasticizer onto both sides of the tow band.

A plasticizer, when employed, will be selected, of course, according to the nature of the filaments. When the preferred cellulose acetate filaments are used, the plasticizer may be triethyl citrate, dimethoxy ethyl phthalate, or methyl phthalyl ethyl glycoate among others; desirably, however, glycerol triacetate (triacetin) is employed. Ordinarily, about 2 to 30% by weight of the plasticizerand preferably about 4 to %will be applied to the filaments.

For the manufacture of cigarette filter tips for use in cigarettes of conventional cross section (i.e. cigarettes having a periphery of about 25 to 26 mm.) the denier per filament will range from about 1 to 50 and preferably from about 1%. to 16, and the total denier of the tow supplied will range from about 20,000 to 160,000, and preferably from about 20,000 to 80,000. The number of crimps per inch will generally be in the range of about 4 to 20, e.g. about 12 to 16.

While the invention finds its greatest utility in the manufacture of cigarette filter rods, it may also be employed in the manufacture of other articles from deregistered crimped tows, e.g. in processes in which a deregistered tow of, say, polyethylene terephthalate filaments, is spread to a wide width (e.g. 3 or 4 feet or more) and then cross-lapped to form a batting material which may be used, for example, for the stufling of pillows.

The filaments of the tow may be made of an organic derivative of cellulose including, particularly, cellulose esters such as the preferred secondary cellulose acetate (e.g. containing about 2 /2 acetyl groups per anhydroglucose unit), as well as cellulose triacetate, cellulose propionate, cellulose acetate propionate, and other cellulose organic acid esters or ethers. Other filamentary materials which may be used include rayon (regenerated cellulose), and filaments of linear superpolyamides such as nylon-6 and nylon-66, linear polyesters (e.g. polyethylene terephthalate), polyolefins (e.g. polypropylene or polyethylene), acrylics (e.g. polyacrylonitrile and known acrylic fibers comprising copolymers of high acrylonitrile content), oxymethylene polymers, polyvinyl chloride (including vinyl chloride copolymers), polyvinylidene chloride (including vinylidene chloride copolymers), nitrile fibers (e.g. vinylidene cyanide-vinyl acetate copolymers), etc.

It is to be understood that the foregoing detailed description is given merely by way of illustration, and that variations may be made therein without departing from the spirit of the invention.

What is claimed is:

1. In an apparatus for the manufacture of cigarette filter tip rods by passing a crimped multifilament tow having crimps in registry through a banding jet, a differential gripping device for deregistering the crimps and for moving said tow longitudinally, and a rod-making machine having a condensing trumpet and garniture, the improvement comprising tow-gripping means in the path of the tow just upstream of the differential gripping device, said tow-gripping means having a first elongated low inertia rolland a second elongated low inertia roll, said first and second rolls being mounted for free rotation, being adapted to engage opposite sides of said tow and to be rotated by the movement of said tow, and having smooth, cylindrical tow-engaging surfaces, a stationary mounting for the first roll, a movable rigid mounting for the second roll, said movable mounting comprising a membercarrying spaced bearings at its ends for rotatably supporting said second roll, means for resiliently urging said movable mounting with a predetermined force in a direction to press said second roll toward the first roll, guide means for constraining said movable mounting to maintain said first and second rolls parallel while said second roll is urged toward said first roll, said guide'means including guide rods secured to said member and projecting from said ends, in a direction perpendicular to said rolls, and stationary bushings for receiving said guide rods, each of said bushings carrying a plurality of circuits of recirculating ball bearings, said urging means having an air chamber supplied with compressed air'and a diaphragm forming a wall of said chamber and operatively connected to said. movable mounting, said differential gripping device having a patterned-surface roll.

2. The apparatus of claim 1 wherein said rolls each have a diameter less than about 2 inches and a weight less than about 5 pounds.

References Cited DORSEY NEWTON,

US. (:1. X.R.

Primary Examiner 

